Variable volume rotary pump



March 1953 T. E. MAHLON VARIABLE VOLUME ROTARY PUMP 2 SHEET SSHEET 1 Filed Oct. 22, 1949 N Q-l mm on A TTORNEYS T. E. MAHLON VARIABLE VOLUME ROTARY PUMP March 10, 1953 2 SHEETSSHEET 2 Filed Oct. 22, 1949 I INVENTOR. TH'oMAs E, MAH LON mm GM ArrokNsYs.

Patented Mar. 10, A 1953 UNITED STATES PATENT OFFICE 2,630,759 VARIABLE VOLUME ROTARY PUMP Thomas E. Mahlon, Allentown, Pa. I Application October 22, 1949, Serial No. 122,891

This invention relatestogear type pumps designed for operation by constant speed motors, and. comprises means for controlling the volume output and the pressure to suit variable conditions of demand and load.

Among the objects of the invention are to provide a simple, efiicient and inexpensive control. system for reducing the volume output of fluid during operation of the pump, and maintain the working pressure, as where lower volume displacement is required to operate hydraulic pressure operated machinery.

Another object is to change the output of pumps subjected to conditions causing overload-,

ing, in order to relieve the motor and prevent stalling and damage to the working parts.

1 Still another object is to provide the more simple sturdy gear type of pump with a variable delivery control system thus adapting an inexpensive type pump for operating hydraulic circuits heretofore requiring more complicated and expensive variable displacement pumps and control units.

With these and other objects in view I have devised an illustrative embodiment of the invention as shown in the accompanying drawings, and hereinafter described and claimed.

In the drawings, Fig. 1 is a plan view of a selfmetering rotary or gear type pump, showing my invention applied thereto; Fig. 2 is a side view and Fig. 3 is an end view of the same; Fig. 4 is a vertical axial section on the line 4-4 in Fig. 1; Figs. 5 and 6 are transverse vertical crosssections on the lines 55 and 6-6 in Fig. 1,

respectively; Fig. 5 showing the gears in side elev'ation; Figs. 7 and 8 are a side View and an inside face view of the end cover plate; Fig. 9 is a cross-section on the line 9-9 in Fig. 6; and Fig. 10 is a vertical axial crossrsection of the by-pass valve for controlling the volume output and pressure of the pump, enlarged scale.

Referring to the drawings, particularly Figs. 4, 5 and 6, the pump shown therein has a base") which supports the pump, shaft II by means of antifriction metal bushings l2, 13 or other suitable bearings mounted in the ends of a suitable cylindrical casing l4 having one end closed by a cap I5 which is removably secured thereto by cap screws or other suitable means as shown in Fig. 2.

- The pump cylinder 18 is formed within the casing l 4 with its axis in alinement with the axis of the pump shaft l l. Inlet and outlet openings i9, 20 communicate through the external wallof the pump cylinder with the inlet and outlet ports 11 Claims. (Cl. 103-42) 2 l, 22, respectively, as shown in Fig. 8, these ports being circumferentially spaced at ninety degrees or so apart around the axis of the pump shaft. The end of the pump cylinder I8 is normally closed by the cover plate or disc [5 which has a circular flange 24 on its inner face projecting into the pump cylinder and provided with a boss or hub' 26 on its outer face containing a bored hole for the idler gear shaft 21. A pin or stud 23 is provided engaging in a complementary hole in the cover for locatingthe two parts of the cylinder in the proper angular position relative to each other for supporting the eccentric idler gear shaft midway between the inlet and outlet ports 2|, 22 as shown in Figs. 3, 4, 5 and 6.

The idler pump gear 28'is mounted on an antifriction metal sleeve 29 which is journalled on the inner end of the shaft 21 and its radial teeth 36 mesh at one side of the pump cylinder be-.

tween the adjacent inlet and outlet ports with the open ended crown teeth 3| which project from the inner face of a disc-like rotor 32 on the inner end of the pump shaft II. The. working faces of the radial teeth 30 are concave and the working faces of the crown teeth 3| are conthe inlet and outlet ports along the cylinder walland between the inner face of the cover projection 24 and the adjacent sides or end faces of the teeth 30.? as well as between the interengaging teeth. The lune shape space in the pump chamber between the points of the teeth 3B, 3! diametrically opposite the circumferential region ofengagement of the teeth is filled by a flange 33 projecting from the inner face of the cover plate 24, thus preventing fluid from passing between the teeth in this region.

Therotor 32 is secured on a bushing 34 which is splined on the inner end of the pump shaft l l to have a capacity for some longitudinal movement with respect thereto while rotating in unison with it, and the rotor 32 is normally held with the" end faces of its teeth 3| in close contact with the inner face of the end, cover plate 2 4 by means of'a coil spring '35 bearing against the bushing l'2 at one end and against'packing washers 36, 31 at. the other end which. in turn engage the inner cupped end of bushing l3.

The bushing I3 is axially adjustable in the opening in the casing l4 and is secured against rotation therein by the screw bolts 38 which pass through th flanges or lugs 39 on the outer end of the bushing and serve to hold the washers 36, 31 in place against the pressure of the spring 35, thereby constituting a leak-proof packing for the end of the shaft H which projects through the bushing IS. The spring 35 also permits axial movement of the rotor 32 to relieve excessive pressure in the cylinder I8 should this be developed to a dangerous extent.

The pump is driven by a motor or engine connected to the shaft I l, and duringnormal operation of the pump as shown in Fig. 2, rotor 32 and idler 28 rotate anti-clockwise, thus-drawing. fluid from suction port 2! and inlet or supply pipe [9 and carrying it between the idler teeth SU-and rotor teeth 3| on either side of abutment 33. As the fluid carrying gear teeth approach discharge port 22 they gradually mesh forcing the fluid through said discharge port and outlet pipe 2.0. until they are completely in mesh at aposition equidistant between the suction and discharge ports and against the inner surfaceof the cylinder wall, forming a barrier to prevent the passage of fluid between said ports.

The volume of fluid passing through the pump is metered by the capacity of the spaces between the successivegear teeth 36 on the idler and 3! on the rotor, and depends upon thespeed of rotation of the pump sha'ft ll, being independent of the pressure within the working range of the pump. Inorder to adjust or control the volume of fluid delivered .per revolution of the pump shaft, .a by-pass pipe in two sections 45, 46 is provided connecting the discharge side of .the pump with the inlet side of the pump, .a shut off valve 41 being located in either section of this pipe to close it when, full volume of discharge is desired. This valve is of any suitable.design,that shown in Figs. 2, 3, .and 10 having a body with a longitudinal bore 48 to which one of the ends of the pipe 45 is connected, and a transverse bore 49 to which the other end of this pipe 45 is connected. The valve plunger 50 is slidable in the longitudinal bore 48 at the inner end or. which is. a seat against which it is held by thespring 52 pressing upon a washer pinned on the inner end of the stem 53, the outer end 54 of which is bent laterally to engage in one or the other end of a bayonet notch formed in the flanged. .extremity 55 of an adjusting thimble 56 screwed into a threaded opening in the end of the casing 41 in axial alinement with the valve. A'lock nut 57 holds the thimble in adjusted position;

In one angular position of thevalve stem its'bent end is in the slot and-the valve is held down on. its seat. In its other angular position the stem can lift against the pressure of the spring 52 to permit opening of the valve. Lighter or heavier springs may be substituted for the spring 52 to control the pressure of the fluid being pumped.

The valve plunger 58 may be lifted voii from its seat by turning the stem 53 out of the bayonet notch slot and raising it against the pressure of the spring 52 and rotating its bent end 54 to engage against the cuter end of the flange 55 to secure it in lifted position, thereby holding the valve open. Thus the valve may be manually set in either closed or open position, or it may be set to open under pressure inthe pump outlet in excess of that for which the spring 52 is adjusted.

The now of fluid through the pipes 45, 46 is uncovers the side port 64, as obviously the spaces between these teeth vary radially from their inner ends which abut the flange 33 to their outer side .faces which abut the inner circumferential wall [,8 of the pump cylinder; and consequently bylocatingthe opening 64 nearer to or farther from the axis of the pump it will be uncovered for a longer or shorter interval of time during the passage of the tooth as seen in Fig. 6, and thus more or less'fluid will be by-passed.

The spring 35, in addition to securing the packing tightly in place and relieving excessive pressure in the pump chamber also serves to maintain. the side faces of the teeth 3| in close contact with the inner face of thecover so as to prevent leakage through the opening 64 as well as to prevent leakage from the inlet to the outlet sides of the pump.

If. desireda plurality of by-pass pipes as. for instance, 45 and 45 46 and 46 and ports or openings 63 63 54 and B4 analogous to the ports. 63 and, 64, each with its own control valve, may be provided, the ports being circumferentially arranged :with spaces between them varying, and each uncovering a, differentareaat each passage of a tooth, so arranged thatone or two or all may be put in operation in sequence or simultaneously and thereby the volume of fluid by-passedmay be correspondingly varied.

The invention is not restricted to the details of construction shown in the drawings, changes in thesize, shape, position and number of passages provided to suit'the type of pump and nature of use to be served being contemplated as within'the scope of the invention.

What is claimed as my invention is as follows:

1. A rotary gear type of fluid pump having a chamber provided with spaced inlet and outlet passages with intermeshing gears disposed between them, and a by-pass connecting said passages for reducing "the volume output of said pump, said by-pass leading through two spaced,

alining .ports in. that portion of the wall of said. chamber whichjencloses. an area of neutral pres sure, said ports being adapted to be covered and u'ncoveredintermittcntly by the teeth of at least.

one of saidgears passing'between them, whereby the'flow through said by-pass. is metered between.

said-gear teeth.

2. A rotary gear'pump as set forth in claim 1 wherein said by-pass is provided with a control valve.

3. A'rotary gear ,pump as set forth in claim '2 wherein there'are a plurality of by-pass passages each with its own control valve.

i. A rotary gear pump 'assetforth in claim 1, wherei n'the lay-pass ports are disposed diametrie. cally opposite to the region of engagement of saidgears. a

5. A rotary gear type of fluidpump having. av

chamber provided with-spaced. inlet andoutlet pa=sages with intermeshing gears disposed .between them connected by a by-pass around said gears, one of said gears engaging the end wall of said chamber with the sides of its teeth, spring means for maintaining said gear in close contact with said end wall, a port in said end wall and another alining port in the side wall of said chamber, said ports being located in an area of neutral pressure opposite the section of said chamber including said inlet and said outlet and adapted to be covered and uncovered by the successive gear teeth passing between them and thereby metering the passage of fluid through said by-pass between said gear teeth.

6. A rotary gear type of fluid pump having a cylindrical chamber provided with spaced inlet and outlet passages disposed at an angle with respect to each other, with intermeshing driving and driven gears filling said chamber between said passages and providing means for pumping a measured amount of fluid at a fixed speed of rotation, said driving gear having inwardly facing teeth arranged circumferentially on the face of a disc rotor to project axially thereof, the outer surfaces of said teeth conforming to the diameter of said chamber and the end faces thereof lying in a plane at right angles to the axis of rotation thereof, an end Wall for said chamber against which the end faces of said teeth bear flatwise, a port in said end wall and an alining port in the side Wall of said chamber, both ports lying in a neutral section of said chamber opposite that bounded by the inlet and outlet passages and in position to be covered by said teeth passing between them as said gear rotates, passages connecting one of said ports with said inlet passage and other port with said outlet passage and means for controlling the flow of fluid through said connecting passages.

7. A gear pump as set forth in claim 6 having automatically operating adjustable means for controlling the flow of fluid through the connecting passages.

8. A gear pump as set forth in claim 7 having manual means for putting said automatically operating adjustable means into and out of operation.

9. A gear pump as set forth in claim 6, having automatically operating adjustable means for controlling the flow of fluid through the connecting passages, and manual means for holding said adjustable means both wide open and fully closed.

10. A rotary gear pump as claimed in claim 1 wherein there are a plurality of by-pass passages, the aligning ports of each by-pass uncovering a different area at each passage of a gear tooth.

11. A rotary gear pump as claimed in claim 10 in which each by-pass carries individual control means whereby said by-pass passages may be individually opened or closed in sequence or simultaneously.

THOMAS E. MAHLON.

REFERENCES CITED The following references are of record in the file of this patent:

- UNITED STATES PATENTS Number Name Date 863,781 Callan Aug. 20, 1907 976,917 Richards Nov. 29, 1910 1,254,060 Mott-lau Jan. 22, 1918 1,913,128 Peter June 6, 1933 2,107,152 Huber Feb. 1, 1938 2,139,373 McKinley et al Dec. 6, 1938 2,159,720 Wahlmark May 23, 1939 2,184,133 Wahlmark Dec. 19, 1939 2,232,983 Wahlmark Feb. 25, 1941 2,309,803 Wahlmark Feb. 2, 1943 2,380,783 Painter July 31, 1945 2,405,061 Shaw July 30, 1946 2,434,135 Witchger Jan. 6, 1948 2,l46,730 Wemp Aug. 10, 1948 FOREIGN PATENTS Number Country Date 325,849 Germany Sept. 21, 1920 378,261 Italy Jan. 27, 1940 

